Kaolin-phosphoric acid polymerization catalyst



Patented Feb. 26, 1952 finesse KAOLIN-PHOSPHORIC ACID POLYMERIZA- TIONCATALYST Jacque C. Morrell, Philadelphia, Pa.

No Drawing. Application November 6, 1947,

Serial No. 784,516

3 Claims. i

'This invention relates to the manufacture and use of catalystsparticularly of the solid granular type which are suitable for organicreactions generally, polymerizing reactions specifically and moreparticularly for the polymerization of oleflns to produce liquids fromgaseous hydrocarbons and/or to increase the molecular weight of thecompounds so treated.

In one specific embodiment the present invention relates to the use ofmixtures of phosphoric acids and china clay or kaolin in admixture forthe treatment of olefin hydrocarbons to polymerize the same-the mixtureof china clay and phosphoric acids being heated or baked to bring abouthardening by combined chemical reactions and removal of water. The acidmay comprise 25 to 75% and more of the final weight of the catalyst.-

The phosphoric acids employed are preferably the orthophosphoric and/orpyrophosphoric acids or mixtures of the same; which may also contain, ifdesired, some free P205, preferably to-a thick syrupy consistency. Thechina clay which contains about'l4% moisture mixes readily with the moreconcentrated acids up to 100% orthophosphoric or above. The heavy pastemay be formed by extrusion or otherwise into suitable shapes and sizes.

The formed catalyst is then dried or baked at temperatures varying from400 to 600 F. depending on the time it is so heated, concentrations ofacids, etc. The lower range may be employed by the special modificationswhich I disclose herein to produce the catalyst directed to lowtemperature quick hardening.

The relatively inert material which may be used in my invention ischinaclay or kaolin (also sometimes referred to a kaolinite) which termsI shall employ alternatively in my invention.

China clay or kaolin is a unique material found in large quantities innature (therefore cheap) and readily distinguishable from and havingdeflnite advantages over other materials heretofore proposed for thispurpose. In this connection I am aware that theprior art discloses theuse of phosphoric acid as a polymerizing agent e. g. E. P. 340,515(1930) discloses the use of phosphoric acid on activated carbon orsilica gel and that later patents have disclosed the use of phosphoricacid with materials of a siliceous character which include diatomaceousearth, kieselguhr and silica gel (artificially prepared porous silica).I, am also aware that certain naturally occurring minerals such asfullers earth, bentonite, montmorillonite and similar mineral adsorbentsubstances which have generally been used as refining agents in thepetroleum industry have been mentioned. However, the use of china clayor kaolin with phosphoric acid has never been disclosed, and 5 none ofthese materials of the prior art have the desirable properties of chinaclay or kaolin as will be apparent from the following characterizationand properties. China clay or kaolin sometimes referred to as alba orwhite bole, terra bole. argilla or porcelain clay is a natural plasticmaterial of remarkably high uniformity in characteristics andproperties.' It is composed of silicon, oxygen and hydrogencorresponding to the general formula: AlzOa2SiOa2HzO. Its origin is fromthe weathering of feldspars.

Kaolin is somethimes referred to as an aluminum-silicate but is probablyall aluminosilicic acid.

It differs from the material of the prior art and can be distinguishedtherefrom in the following important respects. Infusorial earth,kieselguhr and silica gel are siliceous materials 1. e. generallycomposed of silica and oxygen (S102) and are. therefore. entirelydifferent in composition and properties e. g. they lack plasticity andthe property of hardening. Fuller's earth is not a true clay i. e. itlacksplasticity entirely and, is readily fusible unlike china clay.Montmorillonite also has very little plasticity. It is composed largelyof hydrogels of silica and is decomposed by boiling acids e. g. HCl.Bentonite, while highly colloidal; also lacks plasticity. Bothmontmorillonite and bentonite have a much higher silica to alumina ratioand water content than kaolin. They are both amorphous whereas kaolinshows a crystalline x-ray structure.

The materials of the prior art are generally of a porous and adsorbentnature whereas kaolin does not possess these properties and, therefore,

cannot be classified as an adsorbent.

The plasticity of kaolin and its hardening characteristics areattributable to the interlocking of the minute crystals as well aschemical changes as indicated by low temperature transi- 5 tion points,and the loss of water on heating.

Having characterized and differentiated china clay or kaolin from thematerials of the prior art, I shall now proceed to show how it is usedand modified compositions may be made and used in connection with thepresent invention.

Concentrations of orthophosphoric acid from approximately to orpyrophosphoric acid or mixtures thereof together or with P205.metaphosphoric. tetraphosphoric and in general 6 a phosphoric acid inwhich phosphorus has a valence of are employed. These are mixed withchina clay (kaolin) perferably adding sumcient phosphoric acid to thechina clay to obtain the maximum concentration and amount thereof whilepermitting further treatment of the mixture such as forming (byextrusion, etc.), cutting and heating or baking to dry the same. Therelative amounts of kaolin and phosphoric acid may vary roughly between25% to 75% of each, employing the higher proportions with pyrophosphoricacid and mixtures of ortho and P205.

The mixture of phosphoric acid and china clay constitutes a paste ofvarying consistency depending on the temperature of mixing, relativeproportions of the kaolin and phosphoric acid and the kind andconcentration of the latter. Also the application of a relatively smallamount of heat rapidly thickens and congeals the mixture if necessary.The mixture is then formed into pellets, or it may be extruded and cutinto suita-' ble lengths of generally cylindrical or other shapes e. g.to diameter and about length, or broken up into the desirable sizesafter drying or baking. The latter process is carried out at 400 F. to600 F. for one-half to 2 hours, which is referred to as a dryingtemperature range by prior art patents as contrasted with calciningtemperatures of 900 F. at 16 hours for the prior art processes employingsiliceous ma terials and as kieselguhr, infusorial earth and the like.The reason for the relatively mild treatment in the present invention isthe natural tendency for the china clay to set at low tern.- peraturesowing to its plasticity and crystal structure when moistened and heatedand the process as pointed out previously is essentially one of dryingin addition to interlocking of the minute crystals as well as lowtemperature transition points and chemical changes generally, all ofwhich are not possessed by the prior art materials.

When used for polymerizing normally gaseous olefins, the granules orparticles of catalyst are generally placed in treating towers and thegases containing oleflns are passed downwardly through the towers attemperatures of 400 to 500 F. and pressures of several hundred pounds e.g. 100 to 350 lbs. per square inch when employing stabilizer refluxeswhich contain e. g. to 35% of propene and butenes. With gas mixturescontaining normal and isobutene to obtain mixed polymerization thetemperature may be lower e. g. 250 to 350 F. with pressure of 500 to 800lbs. per square inch: Other reactions may be similarly carried out.

It may also be desirable to introduce some steam during the reaction tomaintain the normal vapor pressure of the catalyst; or the gas may besaturated with water vapor.

To remove carbonaceous or hydrocarbonaceous materials which form anddeposit during the treatment the catalysts are reactivated bysuperheated steam and/or air or oxygen at temperatures varying from 500F. to 1000 F. dependent on the concentrations of oxygen. The steamconcentration may be increased toward the end of the burning off periodand then both steam and temperature are decreased toward the very end.These variations in steam concentration and temperature are directedtowards maintaining the proper moisture content or vapor pressure andstructure of the catalyst.

With regard to the structure and hardness of the catalyst which areimportant in the use and life of the catalyst as well as the rate andtem- A amounts of the materials addedshouldbe less than 5% based on thekaolin as they consume acid and in large amounts reduce the hardness andweaken the structure especially calcium oxide. The final products madefrom a mixture containing calcium oxide are softer and also tends totake up moisture more readily than mixtures containing magnesium oxidebut on the other hand are more porous. A mixture of' the two oxides(which ordinarily is found in commercial lime) varying the proportionsgives good results. I have discovered also that zinc oxide has abeneficial effect on the hardness of the catalyst product and ease ofdrying when added to the kaolin to the extent of 1% to- 5% and thehardness and ease of setting will be increased to an even greater extentif zinc chloride is also added to the mixture. The preferred manner ofadding the zinc oxide and zinc chloride is as follows. The zinc oxide isfirst mixed with a small quantity of the kaolin and a concentrated orsyrupy solution of zinc chloride is added. The remaining kaolin admixedwith the phosphoric acid is then combined with the zinc oxide, zincchloride, kaolin mixture. The catalyst resulting from this mixture ishard and dense and can be made more porous by incorporating calciumand/or magnesium oxides to the mixture.

Other additives to the kaolin to improve the properties of the resultingproduct from the viewpoints of quick setting, hardness, structure, etc.are aluminum phosphate (especially if the mixture contains zinc oxide),aluminum or sodium fluorides, copper or zinc silicates and others.

From the viewpoints of economy and control of porosity, hardness andaccelerating setting, I prefer various proportions of calcium andmagnesium oxides taking advantage of the properties imparted by each indetermining the relative proportions of each e. g. as pointed outpreviously calcium oxide produces a more porous product but is softerand takes up water quite readily but these features are corrected by themagnesium oxide. The corresponding carbonates are useful in increasingporosity because of the evolution of carbon-dioxide.

Other chemical reactions such as alkylation. condensation,isomerization, esterlflcatlon, etc. may be carried out also with thesecatalysts or modifications thereof.

The following examples for the preparations and use of these catalystsin polymerizing oleflnic gases are illustrative, but are not to beconstrued as imposing undue limitations upon the broad scope of theinvention.

Example 1 65% by weight of pyrophosphoric acid and 35% by weight ofkaolin were mixed at a temperature of about 325 F. The mixture wasextruded through a die of about diameter and cut into lengths of aboutA". The pieces were then dried at a temperature of approximately 575 F.for about two hours.

Example 2 70% by weight of a mixture containing pyro and orthophosphoricacids and 30% of kaolin containing 5% (by weight of the kaolin) of anequal mixture of magnesium and calcium oxides were admixed and formedafter a short period of warming by extrusion, etc. as in Example 1. Themixture was dried at a temperature varying from 575 F. to 600 F.

Example 3 65% by weight of a mixture of pyrophosphoric andorthophosphoric acids and 35% of kaolin containing 5% of a mixture ofzinc and magnesium oxides were formed and dried as in Example 1.

Example 4 65% of ortho and pyrophosphoric acids were mixed with 25% ofkaolin containing 5% by weight of the kaolin of mixed oxides of calciumand magnesium. To this mixture was added of kaolin containing zinc oxideand zinc chloride prepared as in Example 4 but using about onehalf thequantity. The mixture was formed and dried at about 575 F.

Each modifying substance has its own eifect and, therefore, they are notto be considered as equivalents. However, with all of the catalystsdescribed one may obtain good yields of liquid products whenpolymerizing gases containing olefins such as propenes and butenes. Theconditions of treatment may be between 400 F. to 500 F'. more or lessemploying pressures of several hundred pounds per square inch withstabilizer gases or refluxes containing 10% to 40% of pro penes andbutenes. with normal and isobutene mixtures. lower temperatures may beemployed but the pressures should be somewhat higher as previouslynoted.

The efliciency of the process varies not only with the specificcatalysts and operating conditions but also with the concentrations andtypes of oleflns. The catalyst efllciency may gradually decrease e. g.from about to to less than 10% dependent on the length of use of thecatalyst, the conditions of treatment, etc. The catalyst is finallyreactivated in the ordinary manner by burning off the carbonaceous andhydrocarbonaceous material with oxygen or air and/or steam treatment.

The description and examples are illustrative and are not to beconstrued as restrictive on the broad scope of the invention.

By minor amounts as used in the claims I mean less than 10%.

I claim as my invention:

1. A catalyst suitable for polymerizing olefin hydrocarbons consistingessentially of a mixture of a phosphoric acid and kaolin baked at anelevated temperature prior to the polymerizing process, the said kaolincomprising not less than 25% of the baked mixture.

2. A catalyst suitable for polymerizing olefin hydrocarbons consistingessentially of a mixture of a phosphoric acid selected from the groupcomprising orthophosphoric and pyrophosphoric acids and kaolin baked atan elevated temperature prior to the polymerizing process, the saidkaolin comprising not less than 25 of the baked mixture.

3. A composition of matter suitable for use as a catalyst which consistsessentially of a baked mixture of a phosphoric acid selected from thegroup comprising orthophosphoric and pyrophosphoric acids and kaolin,the said kaolin comprising not substantially less than 25% of the bakedmixture.

JACQUE C. MORREIL.

REFERENCES crrEn The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,993,512 Ipatieif Mar. 5, 19352,020,649 Ipatieff Nov. 12, 1935 2,063,933 Ipatiefl' Dec. 15, 19362,126,282 Rose Aug. 9, 1938 2,324,079 Greger July 13, 1948 2,400,621Alther May 21, 1948 2,415,069 Arvin et a1 Feb. 4. 1947

1. A CATALYST SUITABLE FOR POLYMERIZING OLEFIN HYDROCARBONS CONSISTINGESSENTIALLY OF A MIXTURE OF A PHOSPHORIC ACID AND KAOLIN BAKED AT ANELEVATED TEMPERATURE PRIOR TO THE POLYMERIZING PROCESS, THE SAID KAOLINCOMPRISING NOT LESS THAN 25% OF THE BAKED MIXTURE.